Method for patterning a lanthanum containing layer

ABSTRACT

Embodiments described herein relate to a method for patterning a doping layer, such as a lanthanum containing layer, used to dope a high-k dielectric layer in a gate stack of a FinFET device for threshold voltage tuning. A blocking layer may be formed between the doping layer and a hard mask layer used to pattern the doping layer. In an embodiment, the blocking layer may include or be aluminum oxide (AlO x ). The blocking layer can prevent elements from the hard mask layer from diffusing into the doping layer, and thus, can improve reliability of the devices formed. The blocking layer can also improve a patterning process by reducing patterning induced defects.

BACKGROUND

The semiconductor integrated circuit (IC) industry has experienced rapidgrowth. Technological advances in IC materials and design have producedgenerations of ICs where each generation has smaller and more complexcircuits than the previous generation. However, these advances haveincreased the complexity of processing and manufacturing ICs and, forthese advances to be realized, similar developments in IC processing andmanufacturing are needed. When a semiconductor device such as a finfield-effect transistor (FinFET) is scaled down through varioustechnology nodes, several strategies have been employed to improvedevice performance, such as using high-k dielectric materials and metalgate electrode structures.

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of the present disclosure are best understood from the followingdetailed description when read with the accompanying figures. It isnoted that, in accordance with the standard practice in the industry,various features are not drawn to scale. In fact, the dimensions of thevarious features may be arbitrarily increased or reduced for clarity ofdiscussion.

FIG. 1 is a three-dimensional view of an example of a device inaccordance with some embodiments.

FIGS. 2 through 12 are schematic cross sectional views of a device beingprocessed in accordance with some embodiments.

FIG. 13 includes schematic graphs showing concentrations of aluminum onand/or in a high-k dielectric layer after hard mask removal inaccordance with some embodiments.

FIG. 14 includes schematic graphs showing concentrations of titanium onand/or in a high-k dielectric layer after hard mask removal inaccordance with some embodiments.

DETAILED DESCRIPTION

The following disclosure provides many different embodiments, orexamples, for implementing different features of the provided subjectmatter. Specific examples of components and arrangements are describedbelow to simplify the present disclosure. These are, of course, merelyexamples and are not intended to be limiting. For example, the formationof a first feature over or on a second feature in the description thatfollows may include embodiments in which the first and second featuresare formed in direct contact, and may also include embodiments in whichadditional features may be formed between the first and second features,such that the first and second features may not be in direct contact. Inaddition, the present disclosure may repeat reference numerals and/orletters in the various examples. This repetition is for the purpose ofsimplicity and clarity and does not in itself dictate a relationshipbetween the various embodiments and/or configurations discussed.

Further, spatially relative terms, such as “beneath,” “below,” “lower,”“above,” “upper” and the like, may be used herein for ease ofdescription to describe one element or feature's relationship to anotherelement(s) or feature(s) as illustrated in the figures. The spatiallyrelative terms are intended to encompass different orientations of thedevice in use or operation in addition to the orientation depicted inthe figures. The apparatus may be otherwise oriented (rotated 90 degreesor at other orientations) and the spatially relative descriptors usedherein may likewise be interpreted accordingly.

Embodiments described herein relate to a method for patterning a dopinglayer, such as a lanthanum containing layer, used to tune a high-kdielectric layer in a gate stack of a FinFET device. A blocking layermay be formed between the doping layer and a hard mask layer used topattern the doping layer. In some embodiments, the blocking layer mayinclude or be aluminum oxide (AlO_(x)). Aluminum oxide (AlO_(x)) caninclude any form of aluminum (Al) and oxygen, for example, but notlimited to, aluminum (III) oxide (Al₂O₃), aluminum (II) oxide (AlO), andaluminum (I) oxide (Al₂O). The blocking layer may be deposited between adoping layer containing lanthanum oxide and a hard mask layer containingtitanium nitride. The blocking layer can prevent elements from the hardmask layer from diffusing into the doping layer, and thus, can improvereliability of the devices formed. The blocking layer also can improve apatterning process by reducing patterning induced defects.

FIG. 1 schematically illustrates a device 100 in a three-dimensionalview. Other aspects not illustrated in or described with respect to FIG.1 may become apparent from the following figures and description. Thedevice 100 may be part of an IC, such as a microprocessor, memory cell(such as static random-access memory (SRAM)), and/or other integratedcircuits. In some embodiments, the device 100 includes P-type FinFETstructures 102 formed in an N-doped region 106 a and N-type FinFETstructures 104 formed in a P-doped region 106 b. One or both of theN-doped region 106 a and P-doped region 106 b may be a doped well formedby implantation into a semiconductor substrate. The semiconductorsubstrate may be or include a bulk semiconductor substrate, asemiconductor-on-insulator (SOI) substrate, or the like, which may bedoped (e.g., with a P-type or an N-type dopant) or undoped. In someembodiments, the semiconductor material of the semiconductor substratemay include silicon (Si); germanium (Ge); a compound semiconductor; analloy semiconductor; or a combination thereof.

Fins 110 a and 110 c are formed in the N-doped region 106 a and fins 110b and 110 d are formed in the P-doped region 106 b. The fins 110 a, 110b, 110 c, 110 d can be formed by etching trenches in the semiconductorsubstrate. After formation of the fins 110 a, 110 b, 110 c, 110 d, aninsulating material may be deposited in the trenches between the fins110 a, 110 b, 110 c, 110 d to form isolation regions 108. The isolationregions 108 may include or be an insulating material such as an oxide(such as silicon oxide), a nitride, the like, or a combination thereof.The insulating material may then be recessed such that the fins 110 a,110 b, 110 c, 110 d protrude from between neighboring isolation regions108, which may, at least in part, thereby delineate the fins 110 a, 110c and fins 110 b, 110 d as active areas in the N-doped region 106 a andP-doped region 106 b, respectively.

After formation of the isolation regions 108, dummy gate stacks 150 a,150 b, 150 c, 150 d are then formed on the fins 110 a, 110 b, 110 c, 110d. Each dummy gate stack 150 a, 150 b, 150 c, 150 d includes aninterfacial dielectric 152, a dummy gate 154, and a mask 158. Theinterfacial dielectrics 152, dummy gates 154, and masks 158 may beformed by sequentially depositing respective layers and patterning thoselayers, such as by appropriate photolithography and etch processes. Forexample, the interfacial dielectrics 152 may include or be siliconoxide, silicon nitride, the like, or multilayers thereof. The dummygates 154 may include or be silicon (e.g., polysilicon) or anothermaterial. The masks 158 may include or be silicon nitride, siliconoxynitride, silicon carbon nitride, the like, or a combination thereof.The layers may be formed or deposited by any acceptable technique.

FIG. 1 further illustrates a reference cross-section A-A that is used inlater figures. Cross-section A-A is in a plane along, e.g., channels inthe fins 110 a, 110 b between opposing source/drain regions 156 a-f.FIGS. 2 through 12 are schematic cross sectional views of the device 100along the A-A plane. Particularly, FIGS. 2 through 12 schematicallyillustrate the device 100 at various stages for forming FinFET devicesaccording to some embodiments.

In FIG. 2, gate spacers 115 are formed along sidewalls of the dummy gatestacks 150 a-150 d, e.g., sidewalls of the respective interfacialdielectric 152, dummy gate 154, and mask (not shown). The gate spacers115 may be formed by conformally depositing one or more layers for gatespacers 115 and anisotropically etching the one or more layers. The oneor more layers for the gate spacers 115 may include or be siliconnitride, silicon oxynitride, silicon carbon nitride, the like,multi-layers thereof, or a combination thereof.

After formation of the gate spacers 115, source/drain regions 112 a, 112b may be formed by forming recesses in the fins 110 a, 110 b thenepitaxially growing source/drain materials from the fins 110 a, 110 b inthe recesses. The recesses are formed in the fins 110 a, 110 b onopposing sides of the dummy gate stacks 150 a-d. Recessing can beimplemented by an etch process. The recesses can have variouscross-sectional profiles based on the etch process implemented. Thesource/drain regions 112 a, 112 b may include or be silicon germanium,silicon carbide, silicon phosphorus, pure or substantially puregermanium, a III-V compound semiconductor, a II-VI compoundsemiconductor, or the like. Different materials can be used forsource/drain regions 112 a and 112 b because the source/drain regions112 a are for p-type devices while the source/drain regions 112 b arefor n-type devices. Such different materials can be formed by sequentialprocesses in which appropriate regions are masked during the formationof recesses and epitaxial growth in different fins 110 a, 110 b. In someexamples, the source/drain regions 112 a, 112 b may also be doped, suchas by in-situ doping during epitaxial growth and/or by implantingdopants into the epitaxy source/drain regions 112 a, 112 b afterepitaxial growth. Example dopants can include or be, for example, boronfor the epitaxy source/drain regions 112 a to form p-type devices andphosphorus or arsenic for the epitaxy source/drain regions 112 b to formn-type devices.

After formation of the source/drain regions 112 a, 112 b, a contact etchstop layer (CESL) 114 is formed. The contact etch stop layer 114 canprovide a mechanism to stop an etching process when forming, e.g.,contacts. A contact etch stop layer 114 may be formed of a dielectricmaterial having a different etch selectivity from adjacent layers, forexample, a subsequent interlayer dielectric. The contact etch stop layer114 may be conformally deposited over the epitaxy source/drain regions112 a, 112 b, dummy gate stacks 150 a-d, gate spacers 115, and isolationregions 108. The contact etch stop layer 114 may comprise or be siliconnitride, silicon carbon nitride, silicon carbon oxide, carbon nitride,the like, or a combination thereof.

An interlayer dielectric layer 116 is formed over the contact etch stoplayer 114. The interlayer dielectric layer 116 may comprise or besilicon dioxide, a low-k dielectric material (e.g., a material having adielectric constant lower than silicon dioxide), silicon oxynitride,phosphosilicate glass (PSG), borosilicate glass (BSG),borophosphosilicate glass (BPSG), undoped silicate glass (USG),fluorinated silicate glass (FSG), organosilicate glasses (OSG),SiO_(x)C_(y), Spin-On-Glass, Spin-On-Polymers, silicon carbon material,a compound thereof, a composite thereof, the like, or a combinationthereof.

A planarization process, such as a CMP, may be performed to level thetop surfaces of the interlayer dielectric layer 116 and contact etchstop layer 114 with top surfaces of the dummy gates 154. In someembodiments, a CMP process may be implemented as the planarizationprocess, which may also remove the masks 158 and upper portions of thegate spacers 115. As a result, top surfaces of the dummy gates 154 areexposed through the interlayer dielectric layer 116 and the contact etchstop layer 114, as shown in FIG. 2.

In FIG. 3, the dummy gates 154 and the interfacial dielectrics 152 maybe removed to form trenches 120 a, 120 b, 120 c, 120 d where replacementgate stacks are subsequently formed. The dummy gates 154 may be removedby an etch process, wherein the interfacial dielectrics 152 act as anetch stop. Subsequently, the interfacial dielectrics 152 can be removedby a different etch process.

In FIG. 4, a high-k dielectric layer 122 is formed conformally overbottoms and sidewalls of the trenches 120 a, 120 b, 120 c, 120 d. Insome embodiments, respective interfacial layers 118 may be formed at thebottoms of the trenches 120 a-d prior to forming the high-k dielectriclayer 122 and/or interfacial dielectrics 152 may remain to be theinterfacial layers 118. The interfacial layer 118 may include or besilicon oxide, HfSiO, or oxynitride formed by a proper technique, suchas atomic layer deposition (ALD), chemical vapor deposition (CVD),thermal oxidation, physical vapor deposition (PVD), or UV-ozoneoxidation.

The high-k dielectric layer 122 includes one or more high-k dielectricmaterials. In some embodiments, the high-k dielectric layer 122 includesone of HfO₂, HfZrO, HfSiO, SiO, HfTaO, HfTiO, TiO, Ta₂O₅, which may belater doped with lanthanum. The high-k dielectric layer 122 may beformed by ALD, CVD, metal-organic CVD (MOCVD), another suitabletechnique, or a combination thereof. In some embodiments, the high-kdielectric layer 122 is formed by a blanket, conformal deposition. Thehigh-k dielectric layer 122 may have a thickness in a range from about15 angstroms to about 30 angstroms.

In some embodiments, the high-k dielectric layer 122 includes one ormore hafnium oxide layers formed by an ALD process. For example, thehigh-k dielectric layer 122 may include hafnium oxide, hafnium siliconoxide, hafnium silicon oxynitride, hafnium tantalum oxide, hafniumtitanium oxide, hafnium zirconium oxide, or a combination thereof. Insome embodiments, the hafnium oxide layer may be formed by an ALDprocess using HfCl₄ and H₂O as precursors.

A lanthanum containing layer 124 is formed conformally over the high-kdielectric layer 122. The lanthanum containing layer 124 overlies thehigh-k dielectric layer 122 by a blanket, conformal deposition as shownin FIG. 4. The lanthanum containing layer 124 may be formed by ALD, CVD,MOCVD, or other suitable methods. In some embodiments, the lanthanumcontaining layer 124 may be a lanthanum oxide (La₂O₃) layer. Thelanthanum oxide layer may be formed by an ALD process using a lanthanumsource precursor, such as lanthanum silylamide (La[N(SiMe₃)₂]₃),lanthanum amidinates (for exampleTris(N,N′-di-i-propylformamidinato)lanthanum(III)), and an oxygen sourceprecursor, such as an oxygen (O₂) gas and ozone (O₃) gas with or withouta plasma. In some embodiments, the lanthanum containing layer 124 mayhave a thickness in a range from about 3 angstroms to about 6 angstroms.In some embodiments, the lanthanum oxide layer 124 may be deposited byperforming about 4 cycles to 8 cycles of an ALD process. The lanthanumcontaining layer 124 is implemented as a dopant source for doping thehigh-k dielectric layer 122 in selected regions to tune a capacitanceand/or work function of certain devices, such as in gate stacks forpFinFET structures.

A blocking layer 126 is formed conformally over the lanthanum containinglayer 124. The blocking layer 126 is configured to prevent diffusionbetween the lanthanum containing layer 124 and a subsequent layer, suchas a hard mask layer, during subsequent processes. The blocking layer126 may also improve a patterning process and processing uniformityacross a substrate.

In some embodiments, the blocking layer 126 includes an aluminum oxidelayer formed by an ALD process. For example, the blocking layer 126 mayinclude aluminum oxide (AlO_(x)) formed by an ALD process usingtrimethylaluminum (TMA) and water vapor as precursors. In someembodiments, the blocking layer 126 may be formed by an ALD processusing trimethylaluminum (TMA) and water vapor as precursors for about 10cycles to about 30 cycles. In some embodiments, the blocking layer 126may have a thickness equal to or greater than about 10 angstroms. Forexample, the blocking layer 126 may have a thickness in a range fromabout 10 angstroms to about 30 angstroms, for example, about 15angstroms.

A hard mask layer 128 is formed conformally over the blocking layer 126.The hard mask layer 128 may be used to pattern the lanthanum containinglayer 124 so that the lanthanum containing layer 124 is in selectedregions to dope the high-k dielectric layer 122. The hard mask layer 128can be a titanium containing layer, such as a TiN layer. The hard masklayer 128 may be formed by an ALD process. In some embodiments, the hardmask layer 128 is formed by an ALD process using a titanium sourceprecursor, such as titanium tetrachloride (TiCl₄), and a nitrogen sourceprecursor, such as ammonia (NH₃) and/or hydrazine (N₂H₄). In someembodiments, the hard mask layer 128 has a thickness in a range fromabout 10 angstroms to about 30 angstroms, for example, about 20angstroms.

As discussed above, the blocking layer 126 can provide advantages, suchas improving processing uniformity. In tests, the inventors havediscovered that uniformity of concentrations of titanium and lanthanumacross the substrate (e.g., wafer) can be improved by implementing ablocking layer, like blocking layer 126. Without a blocking layer, itwas discovered that a concentration of titanium can decrease from thecenter of the substrate to the edge of the substrate and that aconcentration of lanthanum can increase from the center of the substrateto the edge of the substrate. With a blocking layer (e.g., blockinglayer 126), it was discovered that respective concentrations of titaniumand lanthanum can be substantially uniform from the center of thesubstrate to the edge of the substrate. With substantially uniformconcentrations of titanium and lanthanum, various subsequent processes,such as etch processes, can have more uniform results across thesubstrate. This can lead to a higher yield of the formed devices.

Referring back to FIG. 4, after formation of the hard mask layer 128, aphotolithography process is performed to pattern the hard mask layer128. In some embodiments, a bottom anti-reflective coating (BARC) layer130 and a photoresist layer 132 may be formed over the hard mask layer128. The BARC layer 130 may be an organic material coated onto thesubstrate filling the trenches 120 a, 120 b, 120 c, 120 d. Aphotolithography process is performed to pattern the photoresist layer132.

In FIG. 5, the BARC layer 130 is patterned using the patternedphotoresist layer 132. A dry etch process may be used to pattern theBARC layer 130 while the hard mask layer 128 serves as an etch stop. Insome embodiments, the patterned BARC layer 130 may expose certainregions, such as regions corresponding to the N-type FinFET structure104 to allow processing over regions of the N-type FinFET structure 104while leaving the remaining regions intact. It is noted that thepatterned layers may be formed at other portion of the substrate, suchas over the N-type FinFET structure 104.

The presence of the blocking layer 126 also shows an improvement inpatterning the BARC layer 130. For example, less BARC residual isobserved in transmission electron microscopy (TEM) images after a BARCdry etch process.

In FIG. 6, the lanthanum containing layer 124 is patterned. Thelanthanum containing layer 124, the blocking layer 126, and the hardmask layer 128 are removed from regions exposed by the patterned layers,for example, the regions over the N-type FinFET structure 104. Thephotoresist layer 132 may be removed, for example, by an ashing process.Portions of the hard mask layer 128, the blocking layer 126, and thelanthanum containing layer 124 that are not underlying the patternedBARC layer 130 or are exposed by the patterned BARC layer 130 can thenbe removed by a suitable etch process.

In some embodiments, the etch process may be a wet etch process. Forexample, the etching process may be performed by dipping, immersing, orsoaking the substrate with or in an etching solution in a wet tank. Theetching solution may be an alkaline, neutral or acid solution with a pHvalue in a predetermined range. Selection of the etching solution isbased on the materials in the lanthanum containing layer 124, blockinglayer 126, and hard mask layer 128. In some embodiments, two or moreetching solutions may be used to etch the hard mask layer 128, blockinglayer 126, and lanthanum containing layer 124 sequentially. In someembodiments, one etching solution may be used to etch all three layers.

In some embodiments, the etching solution(s) may include a phosphoricacid (or orthophosphoric acid), or a mixture of phosphoric acid withother components such as hydrogen peroxide (H₂O₂). Other etchants, suchas hydrofluoric acid (HF), hydrochloric acid (HCl), and/or sulfuric acid(H₂SO₄), may also be utilized. In an example, the ratio of phosphoricacid in deionized (DI) water of the etching solution is in a range fromabout 1:5 to about 1:50. These etchants may be utilized to maintain adesired level of pH value and/or to assist dissociation of the chemicalcompounds dissolved in the etching solution. In an example, the etchingprocess may be maintained at a temperature in a range from about 20 toabout 80 degrees Celsius. Alternatively or additionally, the layers maybe removed by other etch process, such as a dry etch process, such as avapor or a plasma process.

In FIG. 7, the BARC layer 130 is removed by an ashing process, forexample, an ashing process using oxygen plasma.

In FIG. 8, the blocking layer 126 and the hard mask layer 128 areremoved from regions corresponding to the P-type FinFET structure 102,exposing the lanthanum containing layer 124. The blocking layer 126 andthe hard mask layer 128 may be removed by an etch process. In someembodiments, the etch process may be a wet etch process. For example,the etching process may be performed by dipping, immersing, or soakingthe substrate with or in an etching solution in a wet tank. The etchingsolution is selected to have higher etching rates (e.g., higherselectivity) for the blocking layer 126 and hard mask layer 128 than forthe lanthanum containing layer 124.

In some embodiments, the etching solution may include NH₄, H₂O₂, and H₂Oin a ratio of 1:1:5 to etch both layers. In an example, the etchingprocess may be performed at a temperature in a range from about 20° C.to about 80° C., for example at about 60° C. In some embodiments, theetch process may be performed for equal to or greater than 100 seconds,for example in a range from about 150 seconds to 300 seconds. In someembodiments, the etch process may be performed for about 250 seconds.

Because aluminum oxide can be easily removed by acid and base etchchemistry, the aluminum oxide in the blocking layer 126 can enlarge thewindow of etching selectivity between the lanthanum containing layer 124and the hard mask layer 128. As a result, the blocking layer 126 canenable complete removal of titanium in the hard mask layer 128, andthus, can improve threshold voltage tuning in the device.

FIG. 13 includes schematic graphs showing concentrations of aluminum onand/or in a high-k dielectric layer 122 after hard mask removal. Theconcentrations are represented by counts per second (CPS) as a functionof binding energy (eV). Graph 206A is a measurement of aluminumconcentration after the blocking layer 126 is deposited on the lanthanumcontaining layer 124. The blocking layer 126 includes aluminum oxideformed by 15 ALD deposition cycles. Graphs 206B-206F are measurements ofaluminum concentration after the etch processing to remove the hard masklayer 128 and the blocking layer 126 as described above. Graph 206B is ameasurement of aluminum concentration after an etch process using anetching solution including NH₄, H₂O₂, and H₂O at 40° C. for about 150seconds. Graph 206C is a measurement of aluminum concentration after anetch process using an etching solution including NH₄, H₂O₂, and H₂O at40° C. for about 255 seconds. Graph 206D is a measurement of aluminumconcentration after an etch process using an etching solution includingNH₄, H₂O₂, and H₂O at 40° C. for about 330 seconds. Graph 206E is ameasurement of aluminum concentration after an etch process using anetching solution including NH₄, H₂O₂, and H₂O at 60° C. for about 150seconds. Graph 206F is a measurement of aluminum concentration after anetch process using an etching solution including NH₄, H₂O₂, and H₂O at60° C. for about 255 seconds. The graphs 206A-206F demonstrate thataluminum oxide can be easily removed using the etching solution toremove the hard mask layer 126.

FIG. 14 includes schematic graphs showing concentrations of titanium onand/or in a high-k dielectric layer 122 after hard mask removal. Theconcentrations are represented by CPS as a function of binding energy(eV). Graph 208A is a measurement of titanium concentration after a hardmask removal process when there is not a blocking layer formed betweenthe hard mask layer 128 and the lanthanum containing layer 124. Graph208B is a measurement of titanium concentration after a hard maskremoval process when there is an aluminum oxide layer formed from 10cycles of ALD process between the hard mask layer 128 and the lanthanumcontaining layer 124. Graph 208C is a measurement of titaniumconcentration after a hard mask removal process when there is analuminum oxide layer formed from 15 cycles of ALD process between thehard mask layer 128 and the lanthanum containing layer 124. Graph 208Dis a measurement of titanium concentration after a hard mask removalprocess when there is an aluminum oxide layer formed from 20 cycles ofALD process between the hard mask layer 128 and the lanthanum containinglayer 124. Graphs 208A-208D demonstrate that the presence of aluminumoxide blocking layer can improve titanium removal. A thicker layer ofaluminum oxide can provide more improvement than a thinner layer ofaluminum oxide.

Referring back to FIG. 8, after removal of the blocking layer 126 andthe hard mask layer 128, an anneal process is performed. The annealprocess drives lanthanum in the lanthanum containing layer 124 into thehigh-k dielectric layer 122, forming a lanthanum doped high-k dielectriclayer 122′. The anneal process may be performed in a range from about600° C. to about 900° C. In some embodiments, the anneal process may beperformed at about 800° C. In some embodiments, the lanthanum dopedhigh-k dielectric layer 122′ includes lanthanum doped hafnium oxide(LaHfO).

As shown in FIG. 8, the high-k dielectric layer 122 over the P-typeFinFET structure 102 is covered by the lanthanum containing layer 124.The anneal process results in the lanthanum doped high-k dielectriclayer 122′ over the P-type FinFET structure 102 while the high-kdielectric layer 122 (e.g., not doped with lanthanum) remains over theN-type FinFET structure 104. The lanthanum doped high-k dielectric layer122′ may be designed to achieve a desired capacitance and/or workfunction to therefore achieve a desired threshold voltage of the P-typeFinFET structure 102, which can achieve a desired performance. In someembodiments, the lanthanum doped high-k dielectric layer 122′ may have adielectric constant above 7.0.

In some embodiments, the lanthanum doped high-k dielectric layer 122′includes one of HfO₂, HfZrO, HfSiO, SiO, HfTaO, HfTiO, TiO, and Ta₂O₅doped with lanthanum. In some embodiments, the high-k dielectric layer122 may include hafnium oxide, and the lanthanum doped high-k dielectriclayer 122′ includes lanthanum doped hafnium oxide (LaHfO). In someembodiments, the high-k dielectric layer 122 may include hafnium oxide,and the lanthanum doped high-k dielectric layer 122′ includes lanthanumoxide doped hafnium oxide (LaHfO).

After the annealing process, the substrate may be treated to removeunconsumed lanthanum containing layer 124, as shown FIG. 9. Lanthanumcontaining material may be removed by an etch process. In someembodiments, the lanthanum containing layer 124 may be removed by a wetetch process using an acidic solution, such as an aqueous solution ofcarbon dioxide (CO₂), hydrochloric acid (HCl), phosphoric acid (H₃PO₄),acetic acid (CH₃COOH), or other suitable acid solution. The wet etchprocess may be performed at a temperature in a range from about 20° C.to about 80° C., for example at 40° C. The wet etch process may beperformed in a range from about 20 seconds to about 100 seconds, forexample about 60 seconds.

In FIG. 10, a work function layer 134 is formed. The work function layer134 may include Ti, Ag, Al, TiSiN, TiAIN, TaC, TaCN, TaSiN, Mn, Zr, TiN,TaN, Ru, Mo, WN, Cu, W, any suitable material, or a combination thereof.A work function value is associated with the material composition of thework function layer 134. The material of the work function layer 134 ischosen to tune a work function value so that a desired threshold voltage(Vt) is achieved in the device that is to be formed in the respectiveregion. The work function layer 134 may be deposited by CVD, ALD and/orother suitable processes. In some embodiments, the work function layer134 is a TiSiN layer formed by an ALD process. In some embodiments, theALD process may be followed by an anneal process, such as at atemperature of about 850° C. In some embodiments, the work functionlayer 134 has a thickness in a range from about 10 angstrom to about 20angstroms, for example, about 15 angstroms. The thickness of the workfunction layer 134 may be altered and adjusted by altering processparameters during the ALD deposition process, such as the number ofcycles.

In some embodiments, after formation of the work function layer 134 andthe anneal process, a cap layer may be formed over the work functionlayer 134. The cap layer may be a sacrificial layer configured toprotect the work function layer 134 in subsequent processes. In someembodiments, the cap layer may be a silicon layer formed by CVD. In someembodiments, the cap layer may have a thickness of about 30 angstroms.An anneal process may be performed to achieve a desirable work functionvalue. In some embodiments, the anneal process may be performed at atemperature in a range from about 900° C. to about 950° C., for example,about 925° C.

After the anneal process, the cap layer may be removed for furtherprocessing, for example, deposition of gate fill material. In someembodiments, the removal of cap layer may be removed by a dry etchprocess. For example, the cap layer may be removed using a plasma ofetching gas. In some embodiments, the etching gas may include nitrogentri-fluoride (NF₃) and hydrogen (H₂).

In FIG. 11, the trenches 120 a-d may be filled with a conductivematerial 138 for forming gate electrodes therein as shown in FIG. 12.The conductive material 138 may be formed by CVD, ALD, PVD,metal-organic chemical vapor deposition (MOCVD), plating, and/or othersuitable processes. The conductive material may include tungsten (W),cobalt (Co), copper (Cu), aluminum (Al), or a combination thereof.

In FIG. 12, a planarization process, such as a CMP process, is performedafter formation of the conductive material 138 to form top surfaces ofthe conductive material 138 coplanar with the top surface of theinterlayer dielectric layer 116, and thus, form the gate stacks.

The lanthanum doped high-k dielectric layer 122′ in gate stacks in theP-type FinFET structures 102 in FIG. 12 can therefore be doped withlanthanum, while the high-k dielectric layer 122 in gate stacks in theN-type FinFET structures 104 are not doped with lanthanum. Aconcentration of lanthanum in the lanthanum doped high-k dielectriclayer 122′ in the P-type FinFET structures 102 can be in a range fromabout 5 atomic percent (at. %) to about 10 at. %, and the high-kdielectric layer 122 in gate stacks in the N-type FinFET structures 104would be substantially free of lanthanum (e.g., possibly containing anegligible amount as a result of processing, such as described herein).Further, a concentration of titanium (e.g., from hard mask layer 128) inthe lanthanum doped high-k dielectric layer 122′ in the P-type FinFETstructures 102 and the high-k dielectric layer 122 in gate stacks in theN-type FinFET structures 104 can be less than or equal to about 0.1 at.%. A ratio of the concentration of lanthanum to the concentration oftitanium in the lanthanum doped high-k dielectric layer 122′ in theP-type FinFET structures 102 can be greater than or equal to about 50,such as in a range from about 50 to about 100. Hence, processesdescribed herein can enable a high content of lanthanum while permittinga low content of titanium.

The inventors have discovered that, by using a blocking layer in forminga device, a flat band voltage of the device can be increased withdecreased capacitive effective thickness (CET) penalty when compared tomethods that do not implement a blocking layer. Implementing thickerlanthanum containing layers (e.g., by implementing more ALD cycles) canresult in increases in flat band voltages, although the increases in CETcan be greater (but still less than an increase in CET without ablocking layer).

The inventors have further discovered that, based on measurements ofmaximum operation voltage at 125° C. for 10 year lifetime (V_(max)) tocorresponding flat band voltage V_(fb) from a short-loop reliabilitystudy, the lanthanum containing layer processed using an aluminum oxideblocking layer provide positive improvement in device reliability, suchas time dependent dielectric breakdown (TDDB), which may be defined bymaximum operation voltage at 125° C. for 10 year lifetime.

Some advantages of embodiments of the present disclosure includeimproved device reliability, such as improved nTDDB, reduced CET penaltywithout loss of voltage tuning capacity, and improved BARC patterning.

An embodiment of the present disclosure provides a method forsemiconductor processing. The method comprises forming a film stack overa high-k dielectric layer, wherein the film stack includes a lanthanumcontaining layer formed over the high-k dielectric layer, a blockinglayer formed over the lanthanum containing layer, and a hard mask layerformed over the blocking layer, removing the hard mask layer and theblocking layer, and performing an anneal process to drive lanthanum fromthe lanthanum containing layer to the high-k dielectric layer.

Another embodiment of the present disclosure provides a methodcomprising forming a high-k dielectric layer over a substrate, forming alanthanum containing layer over the high-k dielectric layer, forming ablocking layer over the high-k dielectric layer, forming a hard masklayer over the high-k dielectric layer, patterning the hard mask layer,blocking layer, and lanthanum containing, and after patterning thelanthanum containing layer, removing the hard mask layer and blockinglayer.

Yet another embodiment of the present disclosure provides a methodcomprising forming a high-k dielectric layer over a substrate, forming alanthanum containing layer over the high-k dielectric layer, forming analuminum oxide layer over the lanthanum containing layer, forming atitanium nitride layer over the aluminum oxide layer, patterning thetitanium nitride layer, the aluminum oxide layer, and the lanthanumcontaining layer, and after patterning the lanthanum containing layer,performing an etch process to remove the titanium nitride layer and thealuminum oxide layer.

A further embodiment is a semiconductor device. The device includes afirst transistor and a second transistor. The first transistor has afirst fin protruding from a substrate. The first transistor includes afirst gate structure including a first high-k dielectric layer that isover a portion of the first fin and that is substantially free oflanthanum. The second transistor has a second fin protruding from thesubstrate. The second transistor includes a second gate structureincluding a second high-k dielectric layer that is over a portion of thesecond fin and that includes lanthanum. A ratio of lanthanum to titaniumin the second high-k dielectric layer is greater than about 50.

The foregoing outlines features of several embodiments so that thoseskilled in the art may better understand the aspects of the presentdisclosure. Those skilled in the art should appreciate that they mayreadily use the present disclosure as a basis for designing or modifyingother processes and structures for carrying out the same purposes and/orachieving the same advantages of the embodiments introduced herein.Those skilled in the art should also realize that such equivalentconstructions do not depart from the spirit and scope of the presentdisclosure, and that they may make various changes, substitutions, andalterations herein without departing from the spirit and scope of thepresent disclosure.

What is claimed is:
 1. A method for semiconductor processing, the methodcomprising: forming an interfacial layer on a semiconductor material;forming a high-k dielectric layer over the interfacial layer, the high-kdielectric layer extending over the interfacial layer and alongsidewalls of a recess in a dielectric layer, the interfacial layercomprising a different material than the high-k dielectric layer;forming a film stack over the high-k dielectric layer, wherein the filmstack includes a lanthanum containing layer formed over the high-kdielectric layer, a blocking layer formed over the lanthanum containinglayer, and a hard mask layer formed over the blocking layer, wherein theblocking layer comprises aluminum oxide, wherein the hard mask layercomprises titanium nitride; removing the hard mask layer and theblocking layer; and performing an anneal process to drive lanthanum fromthe lanthanum containing layer to the high-k dielectric layer, whereinthe lanthanum containing layer is exposed during the anneal process. 2.The method of claim 1, wherein removing the hard mask layer and blockinglayer comprises: performing a wet etch process using an etching solutionincluding NH₄, H₂O₂, and H₂O.
 3. The method of claim 2, wherein theetching solution comprises NH₄, H₂O₂, and H₂O in a ratio of about 1:1:5.4. The method of claim 2, wherein the wet etch process is performed in atemperature range from about 20° C. to about 80° C. and for a timeperiod in a range from about 150 seconds to about 300 seconds.
 5. Themethod of claim 1, the blocking layer having a thickness in a range fromabout 10 angstroms to about 30 angstroms.
 6. The method of claim 5,wherein forming the film stack comprises forming the blocking layer,forming the blocking layer comprises performing an atomic layerdeposition (ALD) process using trimethylaluminum (TMA) and water vaporas precursors.
 7. The method of claim 5, wherein forming the film stackcomprises forming the lanthanum containing layer, forming the lanthanumcontaining layer comprises performing an ALD process implementing anumber of ALD cycles, the ALD cycles being in a range from 4 cycles to 8cycles, the lanthanum containing layer comprising a lanthanum oxidelayer.
 8. A method comprising: forming a dielectric layer over asubstrate, the dielectric layer having a recess exposing a channelregion of the substrate; forming a high-k dielectric layer over thedielectric layer and over sidewalls and a bottom of the recess; forminga lanthanum containing layer over the high-k dielectric layer; forming ablocking layer over the high-k dielectric layer, the blocking layercomprising aluminum oxide; forming a hard mask layer over the high-kdielectric layer; patterning the hard mask layer, blocking layer, andlanthanum containing layer; after patterning the lanthanum containinglayer, removing the hard mask layer and blocking layer; and afterremoving the hard mask layer and the blocking layer, annealing to drivelanthanum from the lanthanum containing layer into the high-k dielectriclayer, wherein the lanthanum containing layer extends above an uppersurface of the dielectric layer while annealing.
 9. The method of claim8, wherein forming the blocking layer comprises forming the aluminumoxide layer by an atomic layer deposition (ALD) process usingtrimethylaluminum (TMA) and water vapor as precursors.
 10. The method ofclaim 9, wherein the ALD process implements a number of ALD cycles, theALD cycles being in a range from 10 cycles to 20 cycles.
 11. The methodof claim 8, wherein the blocking layer has a thickness in a range from10 angstroms to 30 angstroms.
 12. The method of claim 8, whereinremoving the hard mask layer and the blocking layer comprises using awet etch process.
 13. The method of claim 12, wherein the wet etchprocess is performed using an etching solution including NH₄, H₂O₂, andH₂O.
 14. The method of claim 8, further comprising, after removing thehard mask layer and the blocking layer.
 15. The method of claim 8,wherein the lanthanum containing layer has a thickness in a range from 3angstroms to 6 angstroms.
 16. The method of claim 8, wherein the hardmask layer comprises titanium nitride.
 17. A method comprising: forminga high-k dielectric layer over a first channel region and a secondchannel region of a substrate; forming a lanthanum containing layer overthe high-k dielectric layer over the first channel region and the secondchannel region; forming a blocking layer over the lanthanum containinglayer over the first channel region and the second channel region,wherein the blocking layer comprises aluminum oxide; forming a maskinglayer over the blocking layer over the first channel region and thesecond channel region; removing the masking layer, the blocking layer,and the lanthanum containing layer from over the second channel region;removing the masking layer and the blocking layer from over the firstchannel region; and after removing the masking layer and the blockinglayer from over the first channel region, annealing to drive lanthanumfrom the lanthanum containing layer into the high-k dielectric layer.18. The method of claim 17, further comprising removing the lanthanumcontaining layer after performing the anneal.
 19. The method of claim17, wherein the masking layer comprises titanium nitride.
 20. The methodof claim 17, wherein the lanthanum containing layer comprises lanthanumoxide.